Ok I've done it ... DOHC vs Pushrod

[Feral]

I couldn't label this OHV vs OHC because technically OHC engines are also OHV (even though un-technically people have come to refer to all pushrods as OHV and all S/D OHC's as OHC).

Anyhow this is about DOHC, SOHC is worthless AFAIC.

I want to have this debate. There are some pretty excellent technical minds on this site and I want it all laid out. My understanding is imperfect and thus I am looking for information.

Anyhow let me prefix this by saying I DO believe that DOHC is a superiorly performing configuration, in the end, than a pushrod. However I believe the performance margin to be less than 10% and probably right around 5%.

Anyhow here's what I know about each ... speaking purely from a technical standpoint ($$$ is not an issue here)

DOHC:
Positives:

#1. Better flow, hands down
#2. Allows for different intake and exhaust timings
#3. Facilitates variable valve technology.
#4. Smaller valves = less inertia

Negatives:
#1. Short/fat intake runners (to facilitate flow) reduce low end torque.
#2. More cams mean more friction
#3. More springs mean more friction

Pushrod
Positives:

#1. Long/narrow runners increase velocity and provide excellent low end torque.

Negatives:

#1. Large, heavy valves required to get decent flow
#2. Heavy valvetrain due to pushrods
#3. Single Camshaft limits timing options.
#4. Long/narrow runners decrease flow.


I leave this as a strictly technical discussion as to which performs in a superior manner. I could care less about costs. I am quite positive that DOHC is superior ... but again

[Igetlaidalot]

i woud have to agree that dohc is a superior setup, and you can judge that simply by looking at motors with similar flow characteristics (as similiar as one cam vs 2 cams can be) and judge power output. in the late 60s whene doch v8s were being tinkered with, the power output was incredible, the science wasnt there to make it costworthy or reliable, and so it stayed in museums and the few lucky people who snuck some out of the factory. doch allows for a higher revving motor by creating less rotational stress (by splitting it in half). you can therefore achieve a dohc that will perform similarly to an OHV but will be mroe street friendly, or an all out dohc that will create more power than an ohv. the timing like you mentioned is a great advantage too, allowing application specific tuning to be more of a possiblity.


i see the only major downside to a dohc is the higher rpm range for power, eliminating a lot of low end power. however many ohv racing cams achieve this same disadvantage to a lesser degree with radical cam designs/.

[TunedPort 335]

Maybe I'm lost, but wouldn't a DOHC setup have alot more mass to move, which would make the motor rev slower.

Hemi's use pushrods and have extremely superior head flow, and those were designed back in the 40's I beleive.. The valve setup is similar to that of todays DOHC motors with Intake valve on the intake side, and exhaust vavle on the exhaust side. Although I do see where DOHC can be better and can outperform pushrods, why do top fuel dragsters still run a pushrod/OHV setup? At 6500hp or so...they seem to be doing just fine.

:eh:

Cool post BTW

[H3llphyre]

Number of valves is not a huge issue. It has and will be proven that you can add more valves. The new SBC that will be in the vette is going to have 3 valves per cylinder. Arao (formally Dominion) has a 32V pushrod head. This gives the flow numbers to match DOHC, except less rotating mass (single cam).

As for VVT. There are products out there for this. More or less, it changes the rocker ratio on the fly. Has anyone used em? I don't know, but the technology exists to do this.

More or less, the tech is there (and available) to counter any benefit from DOHC (aside from a seperate cam for exhaust and intake), yet benefit from the less rotating mass of extra cams.

Personally, fuck DOHC and Pushrod engines. I want electronically actuated valves. infinitely variable lift, duration, etc etc etc. Of course, this will require a few changes (more to 48V electrical systems most likely), but I think it is a worthwhile venture. Not only this, but with the right setup, valve float would be something of the past. Solenoid based would require springs, but a twist style motor driven valve actuator would drive the valve up and down.... Meaning you could control this to the limits of the speed of the motor.... Okay, enough from me.

[540Malibu]

2 motors to prove your pushrod theories wrong, BBC and 426 Hemi's, there are no better flowing heads than either of the two, both are capable of spinning 15k rpm with pushrods and a single cam.....also 2 small valves weigh more than one large valve.....

also, OHC motors have just recently broke the 200mph mark in teh 1/4 mile, pushrod motors have been doing it for 40.

[Feral]

Originally posted by 540Malibu
2 motors to prove your pushrod theories wrong, BBC and 426 Hemi's, there are no better flowing heads than either of the two, both are capable of spinning 15k rpm with pushrods and a single cam.....also 2 small valves weigh more than one large valve.....

also, OHC motors have just recently broke the 200mph mark in teh 1/4 mile, pushrod motors have been doing it for 40.

Wow spencer ... very technical response ... thanks for wasting my time. The Mustang 5.0 is still the fastest car with factory body and factory engine (ran a 6.99@202) ... guess that means GM's all suck.

[Feral]

Originally posted by H3llphyre
Number of valves is not a huge issue. It has and will be proven that you can add more valves. The new SBC that will be in the vette is going to have 3 valves per cylinder. Arao (formally Dominion) has a 32V pushrod head. This gives the flow numbers to match DOHC, except less rotating mass (single cam).


2 things.

#1 ... pushrods still have more total inertial loss in the drivetrain ... larger valves and pushrods = more mass to move back and forth = more power loss.

#2. The 3 and 4 valve pushrod heads have even more mass than a standard pushrod. Yes they help alleviate the flow issue but you now have to also redesign you intake tract to be similar to that of a DOHC setup (fat, short runners) which will rob you of your intake velocity which means torque ... just like in a DOHC.



As for VVT. There are products out there for this. More or less, it changes the rocker ratio on the fly. Has anyone used em? I don't know, but the technology exists to do this.

Yes they have a counter to VTEC ... but nothing to compare to the currently available continuously variable valve timing which offers infinite cam profiles ... and specially in DOHC where you can have the exhaust and intake vary at a different rate whereas with the rocker-slide pushrod you cannot.


More or less, the tech is there (and available) to counter any benefit from DOHC (aside from a seperate cam for exhaust and intake), yet benefit from the less rotating mass of extra cams.

Go do some reading and compare the total inertial losses between pushrod and DOHC ... you will be surprised. Here's a quote that might better explain it.


It's all about inertia and breathing here. The key to high specific output (meaning HP per liter, or cu. in.) is breathing and low pumping losses. In the '60's and 70's, to get more HP out of a given displacement a manufacturer would install bigger valves. HP comes from cramming more air and fuel into the cylinder, so a bigger "door" (valve) can let in a bigger air/fuel mixture per stroke . The problem with a bigger valve is that a bigger valve weighs more than a smaller one (assuming the same metallurgy), and this means to control the extra weight as it's flung open is the spring that closes the valve has to be stiffer. A stiffer valve spring (multiplied by the number of valves), means more energy is spent overcoming the valve pressure, thus partially offsetting the gains of a bigger valve. Another disadvantage of a big valve is that at lower RPM's, the intake charge has a lower velocity and low RPM torque and driveability. suffer. Enter a mulitivalve design. Two 30mm valves give more breathing area than a single 60mm one, and each valve weighs less than a 60mm one, as well. I can hear you saying "but TWO 30mm valves weigh more than a single 60mm one!". True, but for each cam lobe, there is less mass to overcome, and the smaller valves don't have to open as far nor do the valve springs have to have as much spring rate. A 4-valve design almost gives you something for nothing, as at lower RPM's the intake velocity is good for each port (they're small ports) so you get good low RPM torque and driveability., while at high RPM's there's sufficient flow (there's two ports) to make good HP. In practice, there



Tag!

[Feral]

Originally posted by 540Malibu
2 motors to prove your pushrod theories wrong, BBC and 426 Hemi's, there are no better flowing heads than either of the two, both are capable of spinning 15k rpm with pushrods and a single cam.....


You do, of course, realize the reason these heads flow so well is because of the Bore size ... nothing more. If you made a pair of 4V (OHC or pushrod) heads at that bore you would get much more flow ... you do know this right?

Apples to apples ...

[TunedPort 335]

Originally posted by Feral
You do, of course, realize the reason these heads flow so well is because of the Bore size ... nothing more.

I disagree man. Like I said earlier, Hemi's are designed sort of like DOHC setup. Intake valve on intake side, exhaust valve on the exhaust side. Kind of like a straight through design.

[Feral]

Originally posted by TunedPort 335
I disagree man. Like I said earlier, Hemi's are designed sort of like DOHC setup. Intake valve on intake side, exhaust valve on the exhaust side. Kind of like a straight through design.

When you are forced to fit circular valves into a circular or even hemispherical area such as that of a head the more valves you have the more space you can displace ... this is why 4 is always better than 2 when it comes to flow ...

[TunedPort 335]

Then why aren't top fuel dragsters runnin DOHC 4 valve setups. I dunno I just don't see where DOHC is significantly better :hmm:

[Feral]

Sigh ... this is really crappy but it shows what I mean.

[H3llphyre]

Originally posted by TunedPort 335
Then why aren't top fuel dragsters runnin DOHC 4 valve setups.

Its against the rules...

[540Malibu]

Originally posted by Feral
Wow spencer ... very technical response ... thanks for wasting my time. The Mustang 5.0 is still the fastest car with factory body and factory engine (ran a 6.99@202) ... guess that means GM's all suck.

yeah? where did you dig that garbage up, fastest street car in the world is a 70 Chevelle big block door slammer running 6.70's

[540Malibu]

Originally posted by Feral
Sigh ... this is really crappy but it shows what I mean.

so now you have twice the shoruded area with twice the hindered flow.

[540Malibu]

Originally posted by Feral
You do, of course, realize the reason these heads flow so well is because of the Bore size ... nothing more. If you made a pair of 4V (OHC or pushrod) heads at that bore you would get much more flow ... you do know this right?

Apples to apples ...

apples to apples,

2 valve SBC heads still out flow their aftermarket 4 valve counterparts

[540Malibu]

ok, pushrod motors making 6000 horse......wheres your DOHC counterpart?

[Feral]

Originally posted by 540Malibu
apples to apples,

2 valve SBC heads still out flow their aftermarket 4 valve counterparts

Um ... in what comparison? I've never seen a comparison where a set of SBC heads can come close to the 4V Arao heads ... even though the Arao heads are a bad joke ... they still flow like a big block ...

[TunedPort 335]

Here's one advantage for pushrods (http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg)

Plus the 302 still outperforms a 4.6 any day of the week (I don't wanna hear none of that 03 Cobra crap), and is about 10x smaller and easier to work on.

[H3llphyre]

Originally posted by TunedPort 335
Here's one advantage for pushrods (http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg)

Plus the 302 still outperforms a 4.6 any day of the week (I don't wanna hear none of that 03 Cobra crap), and is about 10x smaller and easier to work on.

I don't see why engine size should really be a factor. In a NEW car, you shouldn't EVER have to touch the motor. We aren't talking about ease of modibility, we are speaking purely from a science and performance standpoint. Also, figure this. The current cobra isnt the only 32V 4.6... The mark 8's and earlier cobras also had 32V engines. They were able to make decent power with stupid cams.

[Feral]

Originally posted by TunedPort 335
Here's one advantage for pushrods (http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg)

Plus the 302 still outperforms a 4.6 any day of the week (I don't wanna hear none of that 03 Cobra crap), and is about 10x smaller and easier to work on.

Oh you are right. Pushrod motors are smaller, lighter, and have a lower center of gravity ... which is all good for a road-race application ... you are right.

You can't compare the 5.0 to the 4.6 ... different displacement. Regardless ... speaking strictly stock ... the 4.6 in 2002 cobras was making about 325HP while the 5.0 in the '94's was only making about 250 ... pretty big difference. Yes you can mod the hell out of the 5.0 but you can also mod the hell out of a 4.6 ... I wonder which one has better flowing heads stock? I wonder which one flows more air at equal cam lift and duration?

[TunedPort 335]

I understand why a DOHC setup would flow better. But is that extra flow worth it for the extra size and weight?

[Feral]

Originally posted by TunedPort 335
I understand why a DOHC setup would flow better. But is that extra flow worth it for the extra size and weight?

hehe ... that all depends on who you ask. At the moment it doesn't matter ... SBC's are all still pushrod and that isn't ever going to change. GM has a lot to lose by discontinuing the SBC (lots of aftermarket) ... but Ford made the jump. You have companies like Nissan making almost 300HP out of 3.5L's N/A and fully streetable and BMW making 400+ HP out of 5.0L ... both using advanced technology as discussed in here. It is only a matter of time before Ford begins using some VVT in their DOHC cars ... its only a matter of time.

I believe you will probably always see pushrods in trucks (pushrods are better for this application anyhow) ... but in cars ... I dunno. Right now only two sports cars in the world use pushrod ... the Corvette and the Viper ... other than that ... everything else I can think of is DOHC.

[H3llphyre]

Originally posted by Feral
hehe ... that all depends on who you ask. At the moment it doesn't matter ... SBC's are all still pushrod and that isn't ever going to change. GM has a lot to lose by discontinuing the SBC (lots of aftermarket) ...

Um, this i don't understand. GM will not lose the aftermarket by doing anything to the SBC then they already have. The differences between the different generation SBC's are already a prohibitor to the aftermarket. Just for the gen2, the LT1 doesnt have interchangable parts with the block design that immediately preceded it. The LS1 changed this even more. Just in the past 10 years, there have been 3 different SBC's that you more or less, cannot bolt parts in between. I see no problem for them to switch to a DOHC engine, just for what you have stated.


but Ford made the jump.


Yes, but really how many ford engines are DOHC? You have the 4.6 and 5.4 varients, but there are WAY more SOHC 4.6es and 5.4es. Exactly what are the discernable advantages to this setup? I don't really see any, considering the SOHC engines are bigger, heavier, and cost more to manufacture. Sure, there are a few cars that utilize the 32V setup (Cobra, Mark VIII, and Marauder). Ford's "staple" engines are mainly the SOHC setups.


You have companies like Nissan making almost 300HP out of 3.5L's N/A and fully streetable and BMW making 400+ HP out of 5.0L ... both using advanced technology as discussed in here.


This is very true, but you have to ask yourself, or rather discuss, how useful this power is and how long it exists in the power band. Although the 350Z and NSX make damn near close to 300hp out of the 3.5L V6, I tend to wonder how their "average" power compares to similiar sized pushrod V6's. It isnt as easy to state that a 350Z is faster then a grand prix, as their drivetrains are quite different, as are their weight. But, it may stand a chance that the 3.8L V6 in the grand prix puts down more "average" power. Whether or not it is in a uselful range in the power-band to use is another question within itself.

It is only a matter of time before Ford begins using some VVT in their DOHC cars ... its only a matter of time.


Ford does use this already, to my knowledge. They use it in the focus. This isnt alien technology that only the import manufacturers are using. The caddy northstar uses (albeit simplistic) VVT, as do some other domestic engines. Granted, all OHC engines, but still. Not an import thing.



I believe you will probably always see pushrods in trucks (pushrods are better for this application anyhow) ... but in cars ... I dunno. Right now only two sports cars in the world use pushrod ... the Corvette and the Viper ... other than that ... everything else I can think of is DOHC.

Again, untrue. The Lincoln Navigator uses a 32V 5.4L V8. Very similiar to, shit, I want to say the 99 cobra. Maybe it was the 2000, i don't know. Although, it can be argued that the navigator is not a truck, but I believe it is close enough.

[H3llphyre]

Originally posted by TunedPort 335
I understand why a DOHC setup would flow better. But is that extra flow worth it for the extra size and weight?

Well, another factor is the cost difference.

Something to consider. A lot of pushrod engines have cast iron heads. A lot of DOHC engines have aluminum heads. This alone can offset the weight difference. Size isnt a huge issue, unless you want to consider ease of maintenance, which many car companies completely avoid nowadays, because it means more money for them.

Personally I see it as a fuzzy situation. For the normal car out there, I am not convinced that DOHC is a better solution. In terms of econo-boxes and sports cars, this makes sense. First, you want to make the most power you can in a sports car. This means flow. But, people are willing to pay for the added cost and the car can spend more time in design to account for the weight and size. Econo-boxes require the smallest engine running the most efficient, to eak out as much power as they can out of the little fuel they use. Sure, good use, and the SMALL 4 bangers really don't take up THAT much room, as the head is on the top, as opposed to two heads sticking out to the side. But, for normal, daily driven sedans / coupes, I don't know if the added cost is worth the trouble. Most of the problems with the domestics comes from the drivetrain choices. 4 speed autos just aren't going to cut it anymore. Shit, ONLY having autos isnt going to cut it. Just moving to a 5spd auto would solve a LOT of gas milage issues and also putting the power down when it matters.

Anyway, yeah, i kinda went off there... Ah, my point. DOHC is superior, from a technical standpoint. The technology is just the next step, but from a cost and manufacturing standpoint, I don't know if it is always the better route to take. Of course, I am an engineer. At work, I was forced into this ideal. Why do something that is better, when you can use something that is cheaper and gets the job done? I guess thats my point.

[H3llphyre]

Originally posted by Feral
You can't compare the 5.0 to the 4.6 ... different displacement. Regardless ... speaking strictly stock ... the 4.6 in 2002 cobras was making about 325HP while the 5.0 in the '94's was only making about 250 ... pretty big difference. Yes you can mod the hell out of the 5.0 but you can also mod the hell out of a 4.6 ... I wonder which one has better flowing heads stock? I wonder which one flows more air at equal cam lift and duration?

This isnt an "apples to apples" comparison (as you would say). I will use an example. In 1994, the 3.8L V6 that GM uses put down 170hp. The current one puts down 205hp. Thats a 35hp increase, for more or less the same engine. Now, you say a 1994 5.0 put down 250hp. The cobra engine put down 325hp. 75hp difference. The first example is a 20% increase, the second a 30% increase (roughly). So, I have to ask you. Did they change the heads to DOHC in my example to increase the power that much? No. You are talking about a lot of technological advances, OTHER then just heads. Now, lets use a MORE apples to apples comparison. Ford switched over to OHC's. The stock 4.6 puts down about 45hp more then the stock 5.0 put down. Not a HUGE difference. Granted, it is only SOHC, but it is there more or less "standard" V8. It is difficult to compare a newer cobra to the older cobras (where you got your power numbers from). Price wise, there is a MUCH bigger percentage difference from a stock GT to a cobra in 2002, then there was between a stock GT and cobra in 94. Cost, an issue again. I almost think at where we are now with this tech, that DOHC is becoming a "marketting term" more then anything. When you start moving to the higher end cars (mercedes, BMW, etc etc etc), they actually use the DOHC to their advantage, but mainly ONLY in their HIGHEND cars. Need an example, look at a BMW 3-series, power wise, and tell me they are taking full advantage of the DOHC.

[Feral]

Originally posted by H3llphyre
Um, this i don't understand. GM will not lose the aftermarket by doing anything to the SBC then they already have. The differences between the different generation SBC's are already a prohibitor to the aftermarket. Just for the gen2, the LT1 doesnt have interchangable parts with the block design that immediately preceded it. The LS1 changed this even more. Just in the past 10 years, there have been 3 different SBC's that you more or less, cannot bolt parts in between. I see no problem for them to switch to a DOHC engine, just for what you have stated.

The problem isn't so much the engine block ... it's the bellhousing and the bolt pattern on the engine. While the heads have been different between SBCs ... you've been able to bolt different SBC's into all generation of the cars ... or trannies for that matter. A DOHC block would be radically different in size and dimensions and I doubt GM could maintain the same mounting points.



Yes, but really how many ford engines are DOHC? You have the 4.6 and 5.4 varients, but there are WAY more SOHC 4.6es and 5.4es. Exactly what are the discernable advantages to this setup? I don't really see any, considering the SOHC engines are bigger, heavier, and cost more to manufacture. Sure, there are a few cars that utilize the 32V setup (Cobra, Mark VIII, and Marauder). Ford's "staple" engines are mainly the SOHC setups.

SOHC isn't all that bad to be honest ... you can easily make 4 valve, sohc design (this is what the 3rd gen eclipses have) ... you just don't get as much performance out of it. Regardless using SOHC heads so that you can have the option for DOHC for the higher end cars is a marketable idea ...



This is very true, but you have to ask yourself, or rather discuss, how useful this power is and how long it exists in the power band. Although the 350Z and NSX make damn near close to 300hp out of the 3.5L V6, I tend to wonder how their "average" power compares to similiar sized pushrod V6's. It isnt as easy to state that a 350Z is faster then a grand prix, as their drivetrains are quite different, as are their weight. But, it may stand a chance that the 3.8L V6 in the grand prix puts down more "average" power. Whether or not it is in a uselful range in the power-band to use is another question within itself.


Still a 3800 series fanboy eh? First of all the NSX makes 290HP out of 3.2L ... the Nissan only makes 280 out of 3.5 with 14 years more of refinement ... hehe. Regardless both engines easily hand an N/A 3800 series engine it's ass both on the dyno and at the strip. Weight has a lot to do with this (what does a Grand Prix weigh?) ... but the engine does as well. What does a 3800 series engine typically put down N/A?? 220/220? The NSX is 290/220 with .6 less liters and the Nissan is 280/250 with .3 less liters. The powerband on the Nissan gets it a low 14 at 98mph and the NSX hits low 13's at 106 (high mid-high 12's at 110 in Japan where they have the type R's).

Even the supercharged 3800 series get's handily ass-kicked by the jap-crap engines with less displacement and N/A.


Ford does use this already, to my knowledge. They use it in the focus. This isnt alien technology that only the import manufacturers are using. The caddy northstar uses (albeit simplistic) VVT, as do some other domestic engines. Granted, all OHC engines, but still. Not an import thing.

Ford got it from Mazda ... it's a Jap-crap technology and we both know it.


Again, untrue. The Lincoln Navigator uses a 32V 5.4L V8. Very similiar to, shit, I want to say the 99 cobra. Maybe it was the 2000, i don't know. Although, it can be argued that the navigator is not a truck, but I believe it is close enough.

Trucks need torque and while a DOHC can make torque it is better suited to HP. Ford's 6.6L (I think) workhorse in their f-250's is a pushrod ... so is their V10. Pushrod is simply better suited to a truck (actually turbo-deisel is best suited to a truck ... but if you are stick with gasoline you want a standard pushrod). The navigator is bling-bling on wheels ... it isn't a truck (all truck owners on this forum should take offense to this and lynch Jay).

[Feral]

Originally posted by H3llphyre
This isnt an "apples to apples" comparison (as you would say). I will use an example. In 1994, the 3.8L V6 that GM uses put down 170hp. The current one puts down 205hp. Thats a 35hp increase, for more or less the same engine. Now, you say a 1994 5.0 put down 250hp. The cobra engine put down 325hp. 75hp difference. The first example is a 20% increase, the second a 30% increase (roughly). So, I have to ask you. Did they change the heads to DOHC in my example to increase the power that much? No. You are talking about a lot of technological advances, OTHER then just heads. Now, lets use a MORE apples to apples comparison. Ford switched over to OHC's. The stock 4.6 puts down about 45hp more then the stock 5.0 put down. Not a HUGE difference. Granted, it is only SOHC, but it is there more or less "standard" V8. It is difficult to compare a newer cobra to the older cobras (where you got your power numbers from). Price wise, there is a MUCH bigger percentage difference from a stock GT to a cobra in 2002, then there was between a stock GT and cobra in 94. Cost, an issue again. I almost think at where we are now with this tech, that DOHC is becoming a "marketting term" more then anything. When you start moving to the higher end cars (mercedes, BMW, etc etc etc), they actually use the DOHC to their advantage, but mainly ONLY in their HIGHEND cars. Need an example, look at a BMW 3-series, power wise, and tell me they are taking full advantage of the DOHC.


Oh I agree ... the average car doesn't need DOHC. It is better off with it ... but it doesn't need it. The 330 and the M3 both are using that DOHC to their full advantage (333HP out of 3.0L N/A ???)

[Feral]

Shit ... I just realized that if the chevy 350 made as much HP/L and TQ/L as the BMW it would be making 635HP and 425 ft-lbs of TQ ... now that would rule.

Sure you can in fact make a 350 do that ... but not on pump gas and not with a streetable cam ...

[H3llphyre]

Originally posted by Feral
Oh I agree ... the average car doesn't need DOHC. It is better off with it ... but it doesn't need it. The 330 and the M3 both are using that DOHC to their full advantage (333HP out of 3.0L N/A ???)

Again, you are using the high-end sports version as an example, where price matters very little.... The 330 makes 225hp. Yup, thats a decent amount of horsepower, but not a lot for a BMW... I would have a hard time saying they are using the tech to its potential in that car.

[H3llphyre]

Originally posted by Feral
The problem isn't so much the engine block ... it's the bellhousing and the bolt pattern on the engine. While the heads have been different between SBCs ... you've been able to bolt different SBC's into all generation of the cars ... or trannies for that matter. A DOHC block would be radically different in size and dimensions and I doubt GM could maintain the same mounting points.

How many people do you know (other then crazy fucks) that swap in between Tune Port, LT1 and LS1 engines? Not a whole lot. They all end up buying the "proprietary" parts for each. Motor mounts mean VERY little to this discussion.



SOHC isn't all that bad to be honest ... you can easily make 4 valve, sohc design (this is what the 3rd gen eclipses have) ... you just don't get as much performance out of it. Regardless using SOHC heads so that you can have the option for DOHC for the higher end cars is a marketable idea ...


This, I fully agree upon, as Ford has done something that has needed to be done for a LONG time. They made a modular motor that can EASILY swap parts for the basic models of cars and the high end.



Still a 3800 series fanboy eh? First of all the NSX makes 290HP out of 3.2L ... the Nissan only makes 280 out of 3.5 with 14 years more of refinement ... hehe. Regardless both engines easily hand an N/A 3800 series engine it's ass both on the dyno and at the strip. Weight has a lot to do with this (what does a Grand Prix weigh?) ... but the engine does as well. What does a 3800 series engine typically put down N/A?? 220/220? The NSX is 290/220 with .6 less liters and the Nissan is 280/250 with .3 less liters. The powerband on the Nissan gets it a low 14 at 98mph and the NSX hits low 13's at 106 (high mid-high 12's at 110 in Japan where they have the type R's).


I only use it as an example, because I am well versed with it. You do the same with the VR4, so go fuck. :bash: Apples to oranges again. You are comparing a car that both weighs more and has an old design "slushbox" behind it. Now, what i would be interested in is a comparison of both engines, on an engine dyno (so it negates weight and drivetrain differences) and see the difference in "average" power. I'm not saying that the 3800 series engine is better, I'm just saying you have to compare things a little closer. Maybe the 3.5L out of an altima.

Even the supercharged 3800 series get's handily ass-kicked by the jap-crap engines with less displacement and N/A.


Again, there are WAY more factors then engine design.


Ford got it from Mazda ... it's a Jap-crap technology and we both know it.


Eh, this may be true. Just remember. The Big3 were playing with DOHC before the imports were. They also have had VVT variants for almost 10 years (again, I reference the Northstar and Quad4 motors).



Trucks need torque and while a DOHC can make torque it is better suited to HP. Ford's 6.6L (I think) workhorse in their f-250's is a pushrod ... so is their V10. Pushrod is simply better suited to a truck (actually turbo-deisel is best suited to a truck ... but if you are stick with gasoline you want a standard pushrod). The navigator is bling-bling on wheels ... it isn't a truck (all truck owners on this forum should take offense to this and lynch Jay).

I don't see why a DOHC motor can't be made to make low end torque. All it would take it smaller valves, or a less aggressive cam on the exhaust side.... hey, this is what the did with the navigator... Look into it, it is the same engine as the Cobra R, cept different cams.

As for my statement of the navigator being a truck... It is just as much as truck as the F-150 is... The F-150 is the most useless truck on EARTH, and may as well be downgraded to a huge car with two doors and no back seat. Junk I tell you. Absolute junk.

[H3llphyre]

Originally posted by Feral
Shit ... I just realized that if the chevy 350 made as much HP/L and TQ/L as the BMW it would be making 635HP and 425 ft-lbs of TQ ... now that would rule.

Sure you can in fact make a 350 do that ... but not on pump gas and not with a streetable cam ...

Haha, funny arguement. If BMW can engineer so well, why isnt the M5 (current) putting down 555hp at the crank? It SHOULD right, by your calculations. You know as well as I do, that as an engine gets larger in displacement, it isnt nearly as efficient at making power for the street. Also, the new vette due out next year (with the 3V setup) will be making 400hp for the normal version and over 500hp for the Z06 (or whatever it is called). This is all with a "mild" cam. You know as well as I do, that there WILL be cams out there that will bump that engine up towards 600hp after a few years. And it will be more then streetable and run on the same gas that BMW's M series use... premium.

[H3llphyre]

Originally posted by Feral
Shit ... I just realized that if the chevy 350 made as much HP/L and TQ/L as the BMW it would be making 635HP and 425 ft-lbs of TQ ... now that would rule.

Sure you can in fact make a 350 do that ... but not on pump gas and not with a streetable cam ...

if you want to get technical about it, lets swing away....

First off, the M3 making 333hp is a 3.2L, not a 3.0L engine. Making the power comparison to 593hp, not 635hp.

-A camaro and an M3 make more or less the same power at the flywheel. Maro is ABOUT 345hp while the M3 is 333hp.
-The M3 gets worse (by 4mpg) fuel economy then a camaro.
-A camaro (same weight) can rip off a 13.5 second 1/4, which the M3 takes 13.7 seconds... Hmm, which is making more "average" power?

Okay, so whats the point in having the DOHC 3.2L V6? Just to say "I can make the same power as a 5.7". The M3 gets worse fuel economy and costs a SHITLOAD more. Wanna make this comparison even better? Compare it to a base model vette, which can rip off 13.1 second 1/4's and costs the SAME as the M3. Again, beats it for fuel economy and is faster. Yup, it weighs 200lbs less, so thats where the times come from comparing it to the maro.

So, again, I try and prove my point... What's the point of moving to a more expensive technology if you can do it cheaper?


TAG! You're it!

[TunedPort 335]

Most stock LS1's, auto or 6spd, are in low-mid 13's. A handful have pulled very high 12's right down to the paper filter. 28mpg on highway, responds well to mods, etc etc...all using pushrods.

[Feral]

Originally posted by H3llphyre
Haha, funny arguement. If BMW can engineer so well, why isnt the M5 (current) putting down 555hp at the crank? It SHOULD right, by your calculations. You know as well as I do, that as an engine gets larger in displacement, it isnt nearly as efficient at making power for the street. Also, the new vette due out next year (with the 3V setup) will be making 400hp for the normal version and over 500hp for the Z06 (or whatever it is called). This is all with a "mild" cam. You know as well as I do, that there WILL be cams out there that will bump that engine up towards 600hp after a few years. And it will be more then streetable and run on the same gas that BMW's M series use... premium.

You're full of shit. Show me one ... and mean even a single one ... 350CI pushrod SBC that makes 600HP on pump gas N/A with a streetable cam. I mean even one. Fuck it's hard enough getting 500HP out of a SBC and still saying that. You are a shameless GM fanboy ... the new vette this the new vette that ... brag about it when it comes out fanboy.

[Feral]

Originally posted by H3llphyre
if you want to get technical about it, lets swing away....

First off, the M3 making 333hp is a 3.2L, not a 3.0L engine. Making the power comparison to 593hp, not 635hp.

-A camaro and an M3 make more or less the same power at the flywheel. Maro is ABOUT 345hp while the M3 is 333hp.
-The M3 gets worse (by 4mpg) fuel economy then a camaro.
-A camaro (same weight) can rip off a 13.5 second 1/4, which the M3 takes 13.7 seconds... Hmm, which is making more "average" power?

Okay, so whats the point in having the DOHC 3.2L V6? Just to say "I can make the same power as a 5.7". The M3 gets worse fuel economy and costs a SHITLOAD more. Wanna make this comparison even better? Compare it to a base model vette, which can rip off 13.1 second 1/4's and costs the SAME as the M3. Again, beats it for fuel economy and is faster. Yup, it weighs 200lbs less, so thats where the times come from comparing it to the maro.

So, again, I try and prove my point... What's the point of moving to a more expensive technology if you can do it cheaper?


TAG! You're it!

Again ... you stray off topic. Above when I began this post I said $$$ is no issue. This is a technological debate, not a budgetting meeting.

Regardless ... yey a motor with 2.5L more displacement can get .2 faster in the 1/4 ... color me impressed.

I am not an M3 fan and my point wasn't that the M3 is a better car than an F-body. My point was it is using better technology. Arguing gas mileage in a performance contest??? Again ... lame and senseless. My VR4 can get 33mpg and can destroy an LS1 ... does that make it better?? Dumb arguement.

If you want the extreme example lets look at my good friend the McLaren F1. 6.0L, 625HP/550ft-lbs of torque on pump gas and perfectly street friendly. Runs 11.0 stock. Now fuck off and make a real point ... you argue for the sake of arguing and ignore my points ... I consider that highly disrespectful.

[Igetlaidalot]

uuuggghhhh you make thor angry!

[ThaSac (MicZic)]

4.6 owner:

"Hey guy, like my DOHC heads flow soooooooooo much fuckin' air its fuckin unbelievable!"

5.0 owner:

"Hey dude, ur one head is the size of my FUCKING ENGINE!"

Zach

[H3llphyre]

Originally posted by Feral
Again ... you stray off topic. Above when I began this post I said $$$ is no issue. This is a technological debate, not a budgetting meeting.

Regardless ... yey a motor with 2.5L more displacement can get .2 faster in the 1/4 ... color me impressed.

I am not an M3 fan and my point wasn't that the M3 is a better car than an F-body. My point was it is using better technology. Arguing gas mileage in a performance contest??? Again ... lame and senseless. My VR4 can get 33mpg and can destroy an LS1 ... does that make it better?? Dumb arguement.

If you want the extreme example lets look at my good friend the McLaren F1. 6.0L, 625HP/550ft-lbs of torque on pump gas and perfectly street friendly. Runs 11.0 stock. Now fuck off and make a real point ... you argue for the sake of arguing and ignore my points ... I consider that highly disrespectful.

Okay, i managed to ignore the money aspect... I will not dispute that DOHC is far superior to a 2V or pushrod setup for pure performance. There is no beating the type of flow you can get out of 4 valves per cylinder. Big block arguments are pretty much null and void too, cuz if they made DOHC big block heads, they would flow like a motherfucker and make some insane power.

The point I was trying to make, on a stock basis, is that GM can do the same thing as everyone else on their production cars with pushrod, and it costs less.... But, now that it is clear that isnt the point of the argument, I will let it go.

Oh, and 4 valves isnt enough. I want a V10 40V with VVT and a gigantic variable vane, ball bearing turbo. Should be good for like 1200hp on pumpgas.

[H3llphyre]

Oh, and to push more buttons, I still think these two points are wrong...



#1. Large, heavy valves required to get decent flow
#2. Heavy valvetrain due to pushrods


I don't see how a single valve can weigh more then 2... Valves arent solid, and a single valve doesnt have the weight of two stems.... I could see it weighing the same maybe, but not considerably more.

Also, I don't think that pushrods (which are hollow) could weigh more in the drivetrain then 3 extra cams and the extra rockers...

Either way, DOHC is better, just nit picking.

[Feral]

Pay no attention to my previous rage ... I do that sometimes ... I am by no means a rational person unless I have to be (at work ...).

Originally posted by H3llphyre
I don't see how a single valve can weigh more then 2... Valves arent solid, and a single valve doesnt have the weight of two stems.... I could see it weighing the same maybe, but not considerably more.

No two valves typically weigh MORE than one ... true ... but think about the inertia involved ... think about how a valve works and opens ... to swing open one larger valve requires more spring force than two smaller yet slightly heavier ones ... specially in the higher RPMS where these things are opening and closing 40-50 times a second. It's a rotating mass thing ... works the same way with pistons (and is part of why smaller engines are more efficient smaller pistons = less inertia ... why that McLaren is so bad-assed ... V12 with a cylinder dimensions of my VR4 ... just twice as many)


Also, I don't think that pushrods (which are hollow) could weigh more in the drivetrain then 3 extra cams and the extra rockers...

No pushrods don't weigh a lot but they do move a lot and have connectors that lose heat to friction. You are correct that if you took all the head parts of a DOHC engine and weighed them compared to a pushrod's parts the DOHC would be heavier ... but that's mostly cause of the cams (which effectively suffer no inertial losses ... they don't move ... just friction). When you consider the amount of mass that has to reciprocate ... the pushrod moves a lot more metal farther ... hence more energy lost while functioning.